The present invention relates to aerial lift platforms, in combination with apparatus for holding and moving material in position to be worked on by a workman on the platform.
Cranes, in particular vehicle-mounted cranes, have been widely used for handling material, specifically for the lifting of relatively heavy loads of material from one place, and depositing it in position at another place, the lifting and depositing being at locations which are often spaced both horizontally and vertically. When the material has been in place, it is then worked on as necessary by workmen, as by securing it in position, assembling the material or load to some other material or to a structure, or the like.
Aerial lift platforms have been widely used, these being somewhat similar to the above noted vehicle-mounted cranes, and including a vehicle with a boom mounted thereon for both horizontal swinging and vertical luffing movement, the boom carrying at or near its outer end a platform for the workman. Typically, the platform includes a floor and an upstanding protective enclosure or railing, to prevent falling of the workman from the platform. The aerial lift platform apparatus heretofore known has primarily been used for positioning a workman at an elevated location, to enable the workman to perform such tasks as repair, replacement and maintenance of equipment and structures. However, there have been several proposals for providing an aerial lift platform apparatus with material engaging, handling and/or supporting devices, so that material could be both moved and supported, with the workman on the platform in position to perform some function in connection with the material being thus supported.
In Grove U.S. Pat. No. 3,809,180, entitled Aerial Platform Apparatus Having Pipe Grabs, there is disclosed an aerial platform apparatus as above described, the workman's platform being equipped at its forward vertical face with pipe grabs, for engaging and holding a length of pipe. The platform is rotated about a horizontal axis, so that its floor is substantially vertical, thereby placing the pipe grabs at ground level. This occurs with the workman standing near the aerial platform apparatus, and controlling its movements by a remote control device. After the pipe grabs engage a pipe, the aerial platform apparatus is moved, so that the platform floor is horizontal, after which the workman mounts the platform and then raises the platform into position, so as to enable the pipe held by the pipe grabs to be installed, as near the ceiling of a building.
The aerial platform apparatus, as set forth in the above referenced patent, has been successfully used in connection with the installation of overhead sprinkler pipes. However, it is now known that in connection with this apparatus, the requirement that the workman be on the ground while the pipe is being engaged by the pipe grabs may be improved upon, as well as the necessity for supporting the weight of the pipe grabs and the pipe directly from the platform.
In P. R. Bill U.S. Pat. No. 3,286,855, there is disclosed a crane mounted on a vehicle, and provided with a boom extension comprising a beam which supports a workman's platform or bucket, and which also supports a pole guiding and gripping device, the boom extension beam being joined by a hinge to the outer end of the crane boom. At its upper end, the boom extension is provided with a load sheave, so that a cable trained over the load sheave may be secured to a pole, the pole then being hoisted to a substantially vertical position with the gripper encircling it, the workman in the bucket carred on the boom extension then being in position to guide the lifting of the pole and subsequently to perform work in relation to the pole. The construction cannot pick up a pole by the pole guide and gripper, due to the geometry of the crane boom, and the pole cannot be positioned horizontally.